I put a SC remote_desktop.exe together for a friend running 32 bit Intel Win XP. It worked fine unencrypted. Then I put one together using the distributed rc4.key. I understand (now) that you have to generate a new one. Anyway when I tried it with the distributed rc4.key I got:

C:\Program Files\uvnc bvba\UltraVNC\msrc4plugin.dsm is either not designed to run on Windows or it contains and error. Try installing the program again using the original installation media or contact your system administrator or the software vendor for support.

I thought I understood from the http://adamwalling.com/SecureVNC/ that SecureVNC is backwards compatible but I assume I still need to generate a new rc4.key but I don't know how outside of the Viewer (which doesn't work as above).